package com.rpp.session;

import com.rpp.config.BoundSql;
import com.rpp.pojo.Configuration;
import com.rpp.pojo.MapedStatement;
import com.rpp.util.GenericTokenParser;
import com.rpp.util.ParameterMapping;
import com.rpp.util.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MapedStatement mapedStatement, Object... parameter) throws Exception {

        //1创建数据库连接
        Connection connection = configuration.getDataSource().getConnection();

        //2 解析sql
        BoundSql boundSql = getBoundSql(mapedStatement.getSqlText());

        //3 获取预处理statement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4 设置参数
        String paramterType = mapedStatement.getParamterType();
        Class<?> paramterClass = getClss(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            //参数对应字段名称
            String fileName = parameterMapping.getContent();
            //获取字段
            Field declaredField = paramterClass.getDeclaredField(fileName);
            declaredField.setAccessible(true);
            Object obj = declaredField.get(parameter[0]);
            //设置参数值，从1开始
            preparedStatement.setObject(i + 1, obj);
        }
        //5 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        //返回数据类型
        String resultType = mapedStatement.getResultType();
        Class<?> resultClass = getClss(resultType);

        ArrayList<Object> objects = new ArrayList<>();
        //6 解析并封装结果集
        while (resultSet.next()) {
            Object obj = resultClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();

            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(obj, value);
            }
            objects.add(obj);
        }

        return (List<E>) objects;
    }

    @Override
    public int update(Configuration configuration, MapedStatement mapedStatement, Object... parameter) throws Exception {
        //1创建数据库连接
        Connection connection = configuration.getDataSource().getConnection();

        //2 解析sql
        BoundSql boundSql = getBoundSql(mapedStatement.getSqlText());

        //3 获取预处理statement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4 设置参数
        String paramterType = mapedStatement.getParamterType();
        Class<?> paramterClass = getClss(paramterType);

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            //参数对应字段名称
            String fileName = parameterMapping.getContent();
            //获取字段
            Field declaredField = paramterClass.getDeclaredField(fileName);
            declaredField.setAccessible(true);
            Object obj = declaredField.get(parameter[0]);
            //设置参数值，从1开始
            preparedStatement.setObject(i + 1, obj);
        }
        //5 执行sql并返回结果
        int result = preparedStatement.executeUpdate();
        return result;
    }

    /**
     * 完成对#{}的解析工作：1.将#{}使用？进行代替，2.解析出#{}里面的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;
    }

    private Class<?> getClss(String className) throws ClassNotFoundException {
        if (null == className) {
            return null;
        }
        Class<?> aClass = Class.forName(className);
        return aClass;
    }
}
